Typically, a pipe “P” formed to be included in a pipeline includes a steel body “S” covered on its exterior with a fusion bonded epoxy coating (“FBE coating”) to protect the steel body (FIG. 1). (As will be described, embodiments of the invention are illustrated in the balance of the attached drawings.) The FBE coating is an epoxy-based coating that is also used to protect steel in other applications.
Typically, the steel body's exterior surface is completely coated with the FBE coating when the pipe “P” is delivered to the site at which the pipe is to be installed. As is well known in the art, during pipeline construction, the epoxy coating typically is damaged or worn away in relatively small areas, for a variety of reasons. For example, a damaged portion “D” is illustrated in FIG. 1. For the purposes hereof, it will be understood that the “damaged portion” of the coating may include (i) parts of the coating that are scraped or otherwise damaged and are positioned on the steel body, and/or (ii) any regions where the coating had been removed, exposing the steel body.
When repairing the damaged portion (i.e., damaged or removed) of the FBE coating, initially, any damaged epoxy coating still in place is removed, and the steel body is abraded, so that the new epoxy which is positioned on the steel body will bond with the steel body when it is cured. When the damaged portion “D” is removed and the steel body has been suitably abraded, an area “A” of the steel body “S” is exposed. As can be seen in FIG. 1, the area “A” of the exposed steel body “S” is at least partially defined by existing and securely bonded epoxy coating “M”. Those skilled in the art would appreciate that it is important to avoid damaging the bonded coating “M” in the vicinity of the area “A” when repairing the area “A”.
As is well known in the art, it is very important that the area “A” is covered with replacement epoxy that is bonded to the steel. The bonding is achieved when the epoxy is properly cured. The steel body's exterior surface, before installation in the ground or otherwise, is required to be completely covered with the FBE coating, in accordance with specifications.
Heat may be required to be applied in order to prepare the area “A” of exposed and abraded steel for the application of epoxy thereto. (The exposed steel body is required to be at least 3° C. warmer than the dew point when the epoxy is applied.) Once the epoxy is applied, heat is required (i.e., an appropriate amount, for an appropriate time) to cure the epoxy.
In practice, preheating, and also heating the newly-applied epoxy to cure it, so that the epoxy bonds to the exposed steel to form the FBE coating, is a time-consuming and difficult task. The task may be difficult for a variety of reasons. For example, in very cold weather, preheating may take some time. Also, in cold weather, the epoxy must be carefully heated to the appropriate temperature for the necessary time, but without burning the epoxy. In addition, if fluid is flowing through the pipe on which the epoxy is to be cured, the fluid may affect the temperature of the pipe, sometimes in ways that are difficult to anticipate.
In order to cure the epoxy properly, the correct amount of heat is required to be applied, for the correct time period. Neither too much nor too little heat is acceptable. However, the area of pre-existing (securely bonded) epoxy material “M” surrounding the exposed steel in the area “A” is to be disturbed as little as possible.
In the prior art, a heat gun has commonly been used to preheat the area “A” and to cure epoxy on the area “A” of exposed steel. The heat gun typically used is a hand-held electric heat gun. However, in practice the epoxy often is provided with more heat than is appropriate using this method, with the result that the epoxy patch is not properly cured, and does not bond to the steel as required. For instance, the epoxy is sometimes burned using this method.
As is known, the exposed area “A” of the steel body may alternatively be preheated using a propane blowtorch. This is also difficult to control in practice, and may, if not properly controlled, cause the surrounding securely bonded coating “M” to burn. The burned epoxy coating must then be replaced. In addition, use of the propane blowtorch may result in contamination of the exposed area “A”, which is then required to be sandblasted to remove the contamination.
Another prior art device is a generally cylindrical can, open at one end, with a heat source such as a heat gun mounted therein. The advantage of this device is that it positions the heat gun at a generally consistent distance from the steel body and also from the epoxy, so that an appropriate amount of heat is provided. However, in practice, the can tends to overheat, and its rim engaging the pre-existing material “M” conducts heat to such material, thereby causing the material “M” to melt. This requires further repairs, to repair the damage to the material “M”. Also, because the can is cylindrical and it is radially positioned relative to the pipe, the can's rim only partially engages the curved pipe, and heat escapes via the gaps between the pipe and the can, and is therefore wasted.